Revolving anode roentgen ray tube



April 1952 H KEHRLI 2,594,564

REVOLVING ANODE ROENTGEN RAY TUBE Filed June 6, 1950 11y VENT'OQ HANSIZEHRL m G J W A TTORAIE Y5 Patented Apr. 29, 1952 UNITED STATES PATENTOFFICE REVOLVING ANODE ROENTGEN RAY TUBE Hans Kehrli, Zurich,Switzerland Application June 6, 1950, Serial No. 166,429 In SwitzerlandDecember 16, 1948 This invention relates to Rbntgen or X-ray tubes.

In Rt'mtgen-ray tubes it is known to provide a revolving anode to reduceoverheating of the anode material by the cathode rays, which strike theanode material. The X-rays from the anode are, in the use of a directcurrent, of steady uninterrupted radiation and in the use of alternatingcurrent of pulsating radiation according to the frequency employed.

In certain cases, as for example with apparatus for stereoscopic viewsof the bodies penetrated by Rijntgen rays, an intermittent or pulsatingradiation is required from two sources of X-rays which are alternatelyradiated upon the body which is to be investigated. In this case, by theuse of alternating current, the available frequency is exploitedproducing however no satisfactory result, several reasons beingresponsible for this behaviour. One main reason.

is that at the sequence of the'various images in time intervals of onehundredth of one second, the sequently produced images due to theafterglow of the screen appear at times simultaneously in that one imagesince the after-glow is still visible when the other image is about toappear.

It is known to apply two separate X-ray tubes side by side inconjunction with separately driven apertured plates, which are disposedoutside of the tubes. This, however, is inherently disadvantageous inthat, firstly, the distance to the anode cannot be made as small asmight be desirable, and secondly, in that it is difficult to synchronizethe forthcoming of the X-rays with the rotation of the apertured plate.Similar difficulties are involved with revolving anode X-ray tubesprovided with two anodes, and also by tubes with two stationary anodes.In this case, the disposition of the anode plates in front of the tubescauses considerable difficulties, because radiation is disadvantageouslyinfluenced thereby.

The present invention is concerned with a revolving anode X-ray tubewhich is characterized by a revolving apertured plate disposed in theinner space of the tube in which the frequency of radiation from theanode is determined by the rotational speed of the apertured plate.

The appended drawing shows the subject matter of this invention in theway of an example. In the drawing is:

Fig. 1 a schematic illustration in longitudinal section of theinvention,

Fig. 2 shows the apertured disc in front view.

Fig. 3 is the diagram of connections for the X-ray' tube.

' 4 Claims. (Cl. 313--56) In the bulb l which is of glass or any othersuitable material, there are fastened, by means of brackets 2, acylindrical piece 3 and sleeve supports 4 and 5 for the shaft bearing 6of the revolving anode H. The brackets 2 may be secured to the bulb inany suitable manner, e. g. they may be cast to the bulb. The shaft 6 ofthe revolving anode may be journalled in ball bearings disposed in thesleeves 4 and 5.

At the end of the shaft 6 in the enlarged portion of the bulb I, therevolving anode I1 is fitted, the anode consisting of a disc, the edgeof which is as well known formed in such manner that the strikingcathode rays are reflected in the desired direction. In the plane of thedisc diametrically opposed, there are placed two cathodes 1 and 8.

An apertured disc 9 of circular form is also fastened upon the shaft 6of the revolving anode, the disc comprising a concave annular outerportion 9a. The apertured disc 9 has a cut-out sector l0 through whichat rotation of the apertured disc an X-ray beam is emitted.

The revolving anode ll including the shaft 6 and the apertured plate 9are driven by a synchronous motor H disposed in the inner space of thetube.

By the rotational speed of the apertured plate 9 and the number ofcut-out sectors It, the frequency of the X-ray radiation from the anodeI! is determined. The size of one or several cut-out sectors In in theapertured disc 9 determines the period of radiation. In the case of theembodiment shown, the rotational speed of the revolving anode andapertured disc is 1500 revolutions per minute, the apertured disctherefore executes in one twenty-fifth of one second a full revolution,and at the frequency of fifty cycles of the alternating current eachanode produces in each one twenty-fifth of one second one X-ray beam.

Each source of X-ray radiation produces therefore images upon the screenin intervals of one twenty-fifth of one second, whereby the images ofboth sources follow each other in time intervals of one fiftieth of onesecond. The duration of radiation is thereby one hundredth of onesecond.

Hence, the time sequence of the images following each other isindependent of the frequency of the net current and the images are moresuitably conditioned to be readily viewed by the reproducing devices,and are notably more adequately adapted for illustration tov thepeculiar qualities of the human eyes.

The described time sequence has proven to be particularly suitable inregard to the reproduction of stereoscopic images and in regard to thesuppression of after-glow upon the screen. It is understood that byregulation ofthe rotational speed of the revolving anode and apertureddisc the time sequence of the images may be changed within certainlimits. Instead of the two cathodes, as provided for the presentembodiment, a single cathode may be used also. By the use of the X-raytube with only one cathode for the reproduction of stereoscopic imagesof bodies penetrated by X-rays, a second X-ray tube must be employed.This second tube must have the same characteristics as the one alreadydescribed. Such an arrangement permits changing the distance between thetwo sources of X-ray radiation which is useful in certain modes of X-rayapplication. The possibility of variations in the time sequence of theimages and their duration does not suffer by the use of two X-ray tubes.

The revolving anode X-ray tube may be connected without; any diflicultywith the customary transformers (Fig. 3). The corresponding poles of thecathodes are connected in parallel to the high tension winding M of thefilament transformer l3 and the revolving anode 6 is connected with thehigh tension winding 15 of the high tension transformer I 6.

I claim:

1. In a Rontgen or X-ray tube having two cathodes and a revolvable anodecoacting with the cathodes and reflecting the rays in the desireddirection; a disc rotatably disposed in the inner space of the tube. ina plane perpendicular to the path of the reflected rays, the disc havingone aperture coacting with the reflected rays, the speed of the discbeing synchronized with the speed of the anode and determining theintervals of the pulses of the rays issuing from the anode.

2. A Rontgen or X-ray tube comprising a transparent bulb, the bulbhaving a neck at one end and an enlarged portion at the opposite end, acathode disposed through opposite sides of the enlarged portion of thebulb, the inner ends of the cathodes being spaced apart in diametricallyopposed relationship in a plane substantially perpendicular to thecenter line of the bulb, an anode disposed in the bulb intermediate thespaced inner ends of the cathodes, the anode reflecting the rays in thedesired direction, a, shaft for the anode rotatably disposed in the bulbalong the center line thereof, the shaft extending from the neck throughthe anode and protruding therefrom on the side of the enlarged portionof the bulb, means for keying the anode to the shaft, a motor disposedin the neck of the bulb and in operable engagement with the shaft, adisc keyed to the protruding end of the shaft, the disc having at leastone aperture in the path of the refiected rays and coacting therewith,and alternating current means for electrically energizing the anode andcathodes to the emission point of the anode.

3. A Rontgen or X-ray tube according to claim 2 in which the aperture inthe disc is synchronized with the number of cycles per second of thealternating current and the speed of the motor per second to permit thepassage of a ray at intervals greater than one-fiftieth of one second.

4. A Rontgen or Xeray tube according to claim 2 in which the. aperturein the disc is synchronized with the number of cycles per second of thealternating current and the speed of the motor per second to permit thepassage of a ray at time intervals of substantially one twenty-fifth ofone second.

HANS KEHRLI.

REFERENCES CITED The following references are of record in the fileofthis patent:

UNITED STATES PATENTS Number Name Date 1,643,453 Holst Sept. 27, 19272,009,498 Kerr J uly 30, 1935 2,327,586 Atlee Aug. 24, 1943 2,350,642Schwarzer June 6, 1944 FOREIGN PATENTS Number Country Date 315,061Germany Oct. 23, 1919 594,434 Germany Apr. 10, 1934

